The removal of entrained gasses from liquid is an important exercise in a variety of manufacturing and/or analytical processes. An example process in which liquid degassing is widely utilized is in liquid chromatography applications. The presence of dissolved gasses can be undesirable in such applications, wherein the presence of dissolved gasses may interfere with the functionality or accuracy of the application.
In the case of liquid chromatography, for example, it has long been known that the reduction of dissolved air from the chromatographic mobile phase is of critical importance to the stability of system flow rate and, accordingly, to the proper identification of compounds separated by the HPLC system. Dissolved gasses in the mobile phase can manifest in the form of bubbles, which can cause noise and drift in the chromatographic detector. Moreover, the existence of gas bubbles can cause erroneous absorption signatures at the detector.
The degassing of liquid materials has been necessary to the success of many processes, and consequently, various degassing systems and methods have been employed for some time. Techniques have included heating or boiling the fluid to be degassed, exposing the material to a reduced pressure environment or vacuum, and using combination of heat and vacuum to reduce the amount of dissolved gasses in the fluid. Vacuum degassing through a separation membrane has long been known, and generally utilizes a length of relatively small diameter, thin-walled, semi-permeable synthetic polymer barrier contained within an enclosed chamber held under a reduced pressure of vacuum. The fluid to be degassed is typically caused to flow through the lumen of the tubular membrane. Example such apparatus is shown in U.S. Pat. Nos. 5,340,384, 5,183,483, 4,430,098, and 3,668,837.
Other fluid degassing apparatus has been implemented for degassing fluids in fluid transfer lines that operably connect respective components of chromatographic instruments. In such systems, rather than routing the chromatographic fluids into a distinct vacuum chamber for a separate degassing stage, the fluid transfer lines themselves may be configured as tube-in-tube degassers. Example such apparatus is described in U.S. Pat. Nos. 7,713,331; 7,144,443; and 6,949,132, which are assigned to the present Assignee, and the contents of which herein incorporated by reference.
While such transfer line degassing systems have proven to be somewhat effective, certain limitations are inherent with conventional design. For example, the transfer line must oftentimes be flexed into a single or complex curved arrangement in order to appropriately fit between respective instruments in a chromatographic system. Such bending of the transfer line may result in the inner tubular separation membrane deflecting away from the central axis of the transfer line, and even into contact with the outer jacket. Such displacement of the tubular membrane can disrupt fluid flow patterns, thereby diminishing gas transfer efficiency. Moreover, conventional apparatus is typically arranged for “tube-side” degassing, in which the liquidous fluid is passed through the lumen of the tubular membrane, with the tubular membrane being disposed in an evacuated chamber. Degassing capability and efficiency in such an arrangement is limited, and is inferior to a “shell-side” degassing approach, wherein the liquidous fluid is passed through the chamber in surrounding relationship to the tubular separation membrane, with a reduced pressure or sweep gas environment presented in the lumen of the tubular separation membrane.
It is therefore an object of the present invention to provide radial support for substantially centrally positioning one or more tubular degassing membranes within an outer jacket. The radial support may prevent undesired deflection of the tubular separation membrane, and may also permit the use of thinner-walled tubular membranes that are structurally supported within the outer jacket. Reducing wall thickness of the tubular membrane can conserve significant cost to the overall apparatus.